Get list of toggled checkboxes : Angular

I have a few checkboxes. Some of them are selected by default on the basis of data from the database. A user can unselect the selected checkboxes or select the unselected ones. Is there any way to get the list of only those checkbox values which were toggled(this list can be produced on the click of the button once the user finally decide which checkboxes are to be toggled) ?

<ul>
    <li *ngFor="let file of files">
       <input type="checkbox" ng-selected = "file.isPresent"> 
    </li>
</ul>


 <button (click)="getToggledCheckboxValues()"> Get Value </button>

If the file is present already then the checkbox will be checked by default.